Phoronix: LLVMpipe: OpenGL With Gallium3D on Your CPU

The software rasterizer used in Mesa that allows for software acceleration of OpenGL on the CPU without any assistance from the graphics processor has largely been useless. Even with a modern-day, multi-core processor, the performance of Mesa's software rasterizer has been abysmal. The performance of Mesa classic DRI drivers have traditionally been poor anyways compared to the high-performance, proprietary NVIDIA/ATI graphics drivers, but when dealing with just the software rasterizer there really aren't any games or applications that run well. Fortunately, software acceleration on Gallium3D is very much a different story thanks to LLVM.

http://www.phoronix.com/vr.php?view=14871